No takers yet ?
OK, a couple of clues, and another shot of the area shown, with a bit more detail.
It's from a period near to the Proctor, it's a trainer, and a greenhouse with planks for wings would probably look better !!
Hmm - I was thinking DH Drover, but that was single fin, and a different shape at the front end. The twin fins are not what I was tying to identify, now that I've seen the front end.